swept away in the tsunami. and 12-12-12. could this be the luckiest day of the century? thousands of people are counting on it, getting married, even having babies. but can a date make a difference? >> from the global resources of abc news, with terry moran, cynthia mcfadden, bill weir, and tonight, juju chang in new york city, this is "nightline," december 12th, 2012. good evening to you. i'm juju chang. tonight, a baffling portrait is emerging of that mass shooter in oregon who opened fire on a crowd shopping for some holiday cheer. this year, there's been a disturbing number of mass shootings, and investigators say while copycats may be inspired, each shooter has a distinct and chilling back story. we interviewed the 22-year-old's ex-girlfriend, who calls it mind

boggling. >> reporter: chaos amidst the christmas mall rush. lines of shoppers, even children could be seen streaming out with their hands up while a gunman was still inside, announcing from behind a mask, "i am the shooter." a day later, a view of the suspect is now coming into focus. police say 22-year-old jacob tyler roberts was the masked gunman, a young man with no history of serious trouble, who allegedly stole an assault rifle from an acquaintance and set off alone on a deadly rampage. >> we do not understand the motive of this attack, except to say that there's no apparent relationship between the suspect and his victims. >> reporter: hannah sansburn doesn't understand either. >> this is the last thing i would have ever expected. especially from him. he was just too sweet. >> reporter: in an interview with abc news, the shooter's ex-girlfriend told us she has no idea what triggered the sudden and brutal attack.

>> that's what is so mind boggling, because it is -- that was not the person i knew. and the person i knew would never, ever have done anything like this. >> reporter: but there was something strange in recent weeks. he says he seemed numb when she saw him last week, but she didn't think much of it. and she says he suddenly quit his job at a greek deli and sold all of his belongings, telling her he was leaving portland and moving to hawaii this past weekend. >> he had his plane ticket. he was ready to go. and then this happened, and it just makes me think why it was even in the back of his mind or if he just had another plan to leave. >> reporter: instead of hawaii, police say he went to the mall dressed to kill. police say roberts made a beeline from his volkswagen jetta in the parking lot through the macy's store carrying a rifle, wearing a ballistics vest, and a hockey style facemask.

he entered on the upper level, when he got to the food court, he was already reportedly firing, killing 54 hospice nurse cindy ann yuille, who was christmas shopping, and 45-year-old steven forsyth, a father of two, who owned a small business in the mall. he fired into the lower level, hitting this 15-year-old, now in the hospital. there his gun jammed. he bolted down a flight of stairs where he got his rifle working again, according to police, and killed himself near the jcpenney store. it was just the latest rampage in a violent year. july's massacre in aurora, colorado, killed 12, but it wasn't the only mass tragedy. april 2nd, seven dead on a university campus in oakland, california. in august and september, seven dead at a sikh temple in milwaukee, then six dead at a workplace in minneapolis. >> the ability to shoot and kill

other human beings, to actually pull the trigger, requires the shooter look at these humans more as objects than other humans. when you're able to do that, it makes pulling that trigger so much easier. >> reporter: veteran fbi profiler mary ellen o'toole says the triggers for such random violence are not black and white. >> these shooters -- yes, can they have mental health issues? absolutely. but is the reason they're carrying out these crimes because they are mentally ill? i would say no. it's important to make that distinction because most people who are seriously mentally ill are far less violent than the general population. >> reporter: and you had never known him to want to hurt anyone? >> never. never. he never would hurt anybody. i mean, the only way that he would ever get him to be

physically physical with you is if you're tickling him. >> reporter: today, the woman who raised roberts released this picture of the once happy little boy, who police say somewhere along the way turned from happy go lucky to dangerous and unpredictable. a family friend read a statement. >> she has no understanding or explanation for her son's behavior. she's very sad and wants everyone to know she is so sorry what jake did and it's so out of his character. >> reporter: tonight police are running search warrants and chasing down leads. trying to find an explanation for an act of violence that makes no sense. coming up for us, naomi watts on the true story of how one mother risked everything to save her family in that devastating tsunami. captions paid for by abc, inc.

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> "nightline" continues fro new york city with juju chang. p >> yo>> you know >> you king kong's girlfriend. ap and naomi watrand naomi reaching new heights in hollywood with a career built on gutsy performances. her latest movie conjures up the epic title waive, but for one family on vacation, the tsunami of 2004 was a test of survival and the fierce determination of a mother's love. abc's bob woodruff talked to naomi watts for tonight's "nightline" interview. >> reporter: it started out as an idyllic vacation for a young family on the west coast of thailand, a mother and father played by naomi watts and ewan mcgregor and their three young sons. but the holiday soon turns to a living held. and an epic fight for survival in the most devastating natural disaster in modern history.

it was december 26th, 2004, when a giant tsunami swept across southeast asia, destroying entire villages, killing hundreds of thousands. "the impossible" tells the whole story in excruciating detail of what happened to one family caught up with millions of people in the disaster. >> i will find them, i promise you that. >> it just felt like it was rooted in real truth. like every line of dialogue, every detail, everything just felt real. >> reporter: naomi watts plays maria, who along with her son lucas, barely survives the initial wave. maria was badly injured. >> i'm scared. >> reporter: facing unimaginable obstacles, she needs her oldest son to help her and others. >> she was sure that she was

going to die. and so it was absolutely vital to her to impart this need to take care of others. >> we are almost there. we have to get to safety. >> we have to help that boy. >> reporter: the tsunami killed more than 200,000 people and left millions homeless. for those of us covering it, it was one of the most horrific scenes we had ever witnessed. the entire neighborhood as far as the eye can see is completely wiped out. to capture the horror of the event, the director didn't rely solely on computerized special effects. instead, building a huge water tank filled with rushing water and debris. >> we were truly in an uncomfortable situation, which was a massive water tank, being thrust one way, water coming this way, water coming behind you, side pumps, debris, garbage, everything thrown at you. >> reporter: the real family the film is based on are from spain.

lucas is now 18 years old. and maria was deeply involved in the production of the movie. >> we spent hours talking to each other. i wanted to get into her mind, every moment that took place in these 48 hours. >> reporter: in thailand, they filmed in the exact hotel, now rebuilt where they were staying when the tsunami hit. real survivors are in the movie as extras. did you have a chance while you were there in thailand to talk to some of those who survived that moment? >> yes, lots. we were around it every single day. where you're on the set or back at the hotel, there were always reminders of it because everybody was connected to it in some way. >> reporter: watts has very few speaking lines, she says only two pages worth, and conveys all of her emotion in other ways. watts has never shied away from tough roles. >> don't touch me!

get out of my house now! >> reporter: in "21 grams." she wasn't always in demand. >> i was doing endless auditions for years and getting rejected over and over again and really taking a beating on my soul. >> reporter: she landed a role in "mulholland drive" at age 31, old by hollywood standards. >> people said overnight success after "mulholland drive." i went overnight? that's a long night. >> reporter: now 44, she is still getting prime roles in hollywood. >> i feel like the roles are better for women at this age. there's just more than what i girlfriend would be. >> reporter: and there is real buzz over a role she's about to play. princess diana. >> this is a story about a woman who was both complicated, full of contradictions. someone who was fighting for happiness and forced into isolation. >> reporter: in real life, she is happily living with her partner actor liev schreiber and

their two sons. we talked at the top of the crosby hotel. not far from their downtown home. >> i've grown to love new york. it's not an easy straight away. it takes time to get used to this concrete jungle. >> reporter: in february, she might be heading to los angeles for the oscars. >> there's some buzz out there that it's got a good shot. >> well, that's nice buzz. >> reporter: it's not one you can ever deny. >> well, it's always nice, the idea that your peers will recognize you. but it just makes me go all sweaty and clammy and get nervous. >> reporter: for now, watts is staying focused on what happened on that beach in thailand, and the lessons of hope and survival that their story imparts. i'm bob woodruff for "nightline" in new york. >> our thanks to bob woodruff.

"the impossible" opens december 21st, and just today, watts was nominated for a screen actors guild award. the buzz begins. still ahead, are you feeling as lucky as they are? today just may be your day. 12-12-12. ♪ [ engine revs ] ♪ ♪ [ male announcer ] the mercedes-benz winter event is back,

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are you superstitious? then 12-12-12 -- today, that is -- will mean a lot to you. countless people around the globe chose today to buy lotto tickets, schedule c-sections or get hitched. we asked abc's lucky guy, nick watt, to visit the mecca of good fortune, las vegas. >> reporter: we're counting down to midnight to december 12th, 2012. we're in vegas. >> welcome to the world famous little white chapel. in about five minutes, it will be 12-12-12 and all these couples will be married and they'll be happy. >> reporter: if only life were that simple. why are you getting married in the middle of the night in las vegas? >> it's the earliest we could do

it on 12-12-12. >> reporter: special moment follows special molt. >> you may now kiss your bride. >> once in a lifetime and that's what we're supposed to be doing here. >> reporter: your dad got married here? >> yeah, some years ago. one of his marriages. >> reporter: you think it's lucky? >> yeah, it's got to be lucky. >> reporter: why? >> 12 itself is a very spiritual, lucky number. it's a number of completion. >> reporter: really? >> people just really resonate with that strong repetition and symbolism of having one number. >> reporter: we like to look for order in the chaos of life. 12-12-12 is order, so lidty and the numbers won't line up like this again for another 88 years on 01-01-01. fast forward to 12:00 noon, 12 brides and 12 grooms got married at 12 minutes past 12:00.

the brides arrived on a bus. so you're seeing 12-12-12 as a rebirth? >> it is. >> reporter: christina made her own dress. >> the fabric was $12. >> it's my great honor to now pronounce you husband and wife. >> reporter: also today an asteroid passed safely within the shadow of earth and lots of lucky babies were born. this kid popped out at 12 after 12:00. courtney gave birth to a baby boy. >> i feel like 12-12-12 is a lucky day. my husband and i are going to go to vegas and win a lot of cash. >> reporter: meanwhile, back in vegas, matt and mindy got married at the bellagio. are you actually gambling on your wedding day? >> absolutely. we're going to win a lot of money. >> reporter: life's a gamble. marriage is a gamble. are you confident you're going to make this work? >> absolutely. >> love of my life. >> reporter: but if you believe in 12-12-12, whether it means anything or not, just the belief alone might help your chances. i'm nick watt for "nightline" in

las vegas. >> congrats to all. and tonight in new york city, the rolling stones played a benefit concert for the victims of hurricane sandy. and tomorrow night, you can catch them right here on "nightline," where they'll be talking to my very lucky co-anchor bill weir. we hope you check in for "good morning america." we'll see you here tomorrow night. good night. up next on an all-new "jimmy kimmel live" -- >> i haven't been this excited since 11-11-11. >> john krasinski. >> i knew that matt damon was a violent, pompous drunk and now you've proven it on television. >> mike birbiglia. >> now i'll stand for applause. >> the story of christmas as